Recent studies from this laboratry have established that Enterobacteria on the vaginal vestibule determine recurrence of bacteriuria in the adult female, while women immune to urinary infections resist colonization of their introital mucosa. The major aim of this project is to establish the biologic basis for this difference in introital bacteriology between normal women and those susceptible to recurrent bacteriuria. To determine the role of vaginal pH and vaginal antibody, women with recurrent bacteriuria will be followed at frequent intervals to measure (1) the bacterial flora of the vaginal vestibule, urethral and midstream cultures; (2) surface pH of the introital mucosa; (3) glycogen. Using the vaginal model of the adult rabbit, the fate of bacterial inoculation of the vagina is being studied in the normal, oophorectomized rabbit, and hysterectomized rabbit. The role of vaginal and serum factors in colonization of the vaginal mucosa with Enterobacteria is under study.